Production of ribbed building board



Originai Filed Aug. 22; 1963 Jan. 17, 19 7 J. PAGE ETAL 3,298,888

PRODUCTION OF RIBBED BUILDING BOARD 7 Sheets-Sheet l Jan. 17, 1967 J.PAGE ETAL 3,298,888

PRODUCTION OF RIBB ED BUILDING BOARD Original Filed Aug. 22 1963 7Sheets-Sheet 2 Jan 17,1967 J. PAGE ETAL I PRODUCTION OF RIBBED BUILDINGBOARD Original Filed Aug. 22, 1965 7 Sheets-Sheet 3 JFCWMS agmaw Jan.'17, 1967 P ETAL 3,298,888

PRODUCTION OF RIBBED BUILDING BOARD ori inal Filed Aug. 22, 1965 h tyan'fape fab 00:15 jcaq J.PAGE ETAL I 3,298,888

7 Sheets-Sheet 5 Jrtdcrcw Q/M lz/m Jan. 17, 1967 PRODUCTION OF RIBBEDBUILDING BOARD Original Filed Aug. 22, 1963 7 Jan. 17,1967 J. PAGE ETALPRODUCTION OF RIBBED BUILDING BOARD al Filed Aug. 22, 1963 Zyf 7Sheets-Sheet 6 Origin 1&2

PRODUCTION OF RIBBED BUILDING BOARD ori inalrilea Aug. 22, 1963 7Sheets-Sheet 7 II' IJ A I 'll J94 United States Patent 3,298,888PRODUCTION OF RIBBED BUILDING BOARD John Page, Glenview, and Rupert J.Straub, Lisle, Ill., assignors to United States Gypsum Company, Chicago,Ill., a corporation of Delaware Original application Aug. 22, 1963, Ser.No. 303,794. Divided and this application Aug. 12, 1965, Ser. No.

9 Claims. (Cl. 156-347) This application is a division of applicantscopending application Serial No. 303,794, filed August 22, 1963,entitled Production of Ribbed Building Board or the Like, now US. Patent3,260,635.

This invention relates to a process and apparatus for constructing animproved gypsum building board or the like. More specifically, itrelates to a process and apparatus which has rendered feasible for thefirst time the high-speed, low-cost manufacture of a novel ribbedbuilding board having a gypsum core with paper faces, which process andapparatus successfully cope with problems associated with prior attemptsat production of same.

Those skilled in the art have long sought a highspeed method andapparatus for inexpensively producing a gypsum-containing building boardhaving longitudinal ribs on one side and a substantially smooth face onthe opposite side suitable as a finished surface. Such boards may, forexample, be secured individually to a supporting structure to provide afinished surface; or two of such boards may be cemented or otherwisesecured together, preferably rib to rib, to form a building panel suchas a non-load-bearing studless partition or the like.

Prior-art efforts have been largely unsuccessful because of thedemanding process and apparatus requirements to achieve a successfulstructure of the type desired. For example, the face surface of such astructure must be substantially flat. The increase cross-sectional areaat rib locations, however, often results in slight but unacceptabledepressions on the face side coextensive with the ribs because ofdifferential shrinkage during drying of the gypsum. Accordingly, anysuccessful process or apparatus must cope with such difficulty.

Akin to the problem of depressions associated with differentialshrinkage is the problem of unsightly depressions (or protrusions)associated with undersized (or oversized) ribs. For example, to securean undersized rib to a supporting surface or to a mating ribbed buildingboard, the finished surface thereof must be flexed inwardly coextensivewith the undersized ribs so that the rib can make contact. To avoid suchproblem, the production method and apparatus must insure that all ribsare substantially uniform in height as measured from the face side.

Moreover, the rib-side paper must have suflicient paper coextensive withthe longitudinal rib locations to provide protruding envelopes for theribs. Present-day, highspeed production techniques also require thatsuch ribside web be longitudinally fed in non-rectilinear directionsduring formation of the board. Because of the three-dimensionalconfiguration of the rib-side web, however, a substantial change indirection would tend to cause tearing or distortion of the paper. Asuccessful process and apparatus should therefore permit non-rectilinearpaper travel without such tearing or distortion.

Another problem arises from the fact that the rib envelopes must befilled with the gypsum slurry when the slurry is substantially fluid.The ribs must also be shaped and gauged as to height while the gypsumslurry is still substantially plastic. Yet, the ribs, once formed mustnot collapse or otherwise become misshapen. These conflictingrequirements must also be met by any proposed process and apparatus.

Once the ribbed building board is complete, it must Severing bladesemployed for such purposes with conventional, non-ribbed building boardswould cause substantial and unacceptable damage to a ribbed structure.Accordingly, any proposed method and apparatus must permit thehigh-speed segmenting of a ribbed building structure without suchdisability.

In addition, the above and other requirements must be met by a methodand apparatus which permits high-speed, high-volume continuousproduction of the product so that the ultimate installed cost is atleast competitive with alternative constructions. Still further, themethod and apparatus should also lend themselves to adoption withoutbasic modification of present-day, continuous gypsum board productionmachinery, which represents a substantial proportion of the entirecapital investment of the industry today.

These and other requirements are met by the process and apparatus of thepresent invention, as hereinafter described. In brief, the presentprocess in one embodiment is an improvement on the conventionaltechnique wherein a paper sheet is conveyed on a flat belt, calcinedgypsum slurry is deposited thereon, and a cover sheet is addedsimultaneously with the passage of the assembly through avertically-constricted passage, whereby a head of slurry is maintainedjust ahead of the passage. This conventional technique is modified inthat the upper surface of the passage is constituted a contoured memberwhich causes the cover sheet to assume a contour correspondingsubstantially thereto. The slurry is introduced between the sheets insufficient volume to fill the contoured cover sheet, and the assembly soformed is maintained with the cover sheet upward facing at least untilthe slurry has become self-supporting.

After the slurry has become self-supporting and while still plastic, theassembly is passed through a second vertically-constricted passage. Thevertical distance of the second vertically-constricted passage isslightly less than the maximum height of said contoured assembly,whereby rib height above the belt is gauged to a desired uniform value.

In a more specific embodiment of the process of the present invention,two continuous, elongated webs of paper are provided, one web being aface-side web and the other web being a rib-side web. The rib-side webwhile travelling longitudinally is subjected at transverselyspacedintervals to forces in a convergent direction whereby folds or pleatsare progressively induced intermediate the spaced intervals, said pleatscorresponding to desired rib locations. The rib-side web is then alignedfrom a convergent direction with, and in spaced relation opposed to, theface-side web with a fluid calcined gypsum slurry therebetween and incontact therewith. The fluid slurry is forced into the folded portionsof the rib-side web to form a plurality of ribs, preferably under theinfluence ,of subatmospheric pressures exterior to the folded portions.

The resulting ribbed assembly is then flatly disposed with the rib-sideweb upward facing at least until the gypsum slurry obtains sufficientset to retain a flat face on face side. The ribs are shaped to thedesired configuration while the gypsum slurry is still plastic andsupported in such configuration until the slurry is substantiallyself-supporting. Rib height is also adjusted to a uniform distance fromthe face-side web while the gypsum 5 slurry is still plastic butotherwise capable of retaining the distance so gauged. 7

These and other embodiments of the process will become apparent from thefollowing detailed description of certain specific embodiments ofapparatus for carrying out same presented in the accompanying drawingswherein:

FIG. 1 is a diagrammatic side elevation view of an apparatus constructedin accordance with one embodiment of this invention;

FIG. 2 is a diagrammatic top plan view of portions of the apparatusshown in FIG. 1;

FIG. 3 is a perspective view illustrating a portion of a panel formed bycementing together two building boards of the type produced by theapparatus of FIGS. 1 and 2;

FIG. 4 illustrates a grooving roll as well as a portion of one side ofthe rib-side paper grooved thereby, said grooving roll optionally beingemployed in the apparatus of FIGS. 1 and 2;

FIG. 5 illustrates another grooving roll and a portion of the other sideof the rib-side paper grooved thereby, said grooving roll alsooptionally being employed in the apparatus of FIGS. 1 and 2;

FIGS. 6, 7 and 8 are partial sectional views showing details of theapparatus of FIGS. 1 and 2 whereby pleats are induced in the rib-sidepaper, progressive steps in pleat formation being illustrated in saidFIGS. 68;

FIG. 9 is a blown-up view showing the flattening of the pleats formed asshown in FIGS. 68;

FIG. 10 is a perspective view, partly in section, of the master-formingroll and associated structures employed in the apparatus of FIGS. 1 and2, whereby the flattened pleats of the rib-side paper are initiallyunfolded and filled with gypsum to form the ribbed board;

FIG. 11 is a similar perspective view, partly in section, of analternate forming plate for initial rib formation, which plate andassociated structures may be employed in place of the master-formingroll of FIG. 10;

FIG. 12 is a similar perspective view, partly in section, of analternate system employing a series of continuous belts for initial ribformation, which system may also be employed in place of themaster-forming roll of FIG. 10;

FIG. 13 is a view taken along section line 13-13 of FIG. 12;

FIG. 14 is a section view of still another alternative system forinitial rib formation wherein two rolls with intermediate vacuum meansare employed, which system may also be employed in place of themaster-forming roll of FIG. 10;

FIG. 15 illustrates by solid and dashed lines the unfolding of thepleated and flattened rib-side paper which occurs in the master-formingroll of FIG. 10, the forming plate of FIG. 11, or the alternate systemsof FIGS. 12-14;

FIG. 16 is a perspective view, partly in section, showing a portion ofone set of the contour "bars used to shape and support the ribs formedas illustrated in FIGS. 10-14;

FIG. 17 is a transverse elevational view, partly in section, of anotherportion of the contour bars of FIG. 16;

FIG. 18 is a diagrammatic view, partly in section, of the gauging rollof the apparatus of FIGS. 1 and 2 whereby rib height above the face sideis gauged to a predetermined uniform value;

FIG. 19 illustrates a typical rib configuration after the shapingoperation of FIGS. 16 and 17 and the gauging operation of FIG. 18;

FIG. 20 is a diagrammatic view of the severing means of the apparatus ofFIGS. 1 and 2, said severing being employed to segment the resultingribbed building board;

FIG. 21 is an enlarged view of a portion of the blades employed in thesevering means of FIG. 20, the upper blade being notched or contoured ata rib location;

FIGS. 22 and 23 diagrammatically portray the step of routing, which isoptionally employed in the apparatus of FIGS. 1 and 2 to remove ribportions adjacent the ends of the segmented building boards;

FIG. 24 shows a perspective view of the type of routing cutter which maybe employed for rib-end removal, as shown in FIGS. 22 and 23;

FIG. 25 illustrates an alternate construction which may be formed withthe apparatus of FIGS. 1 and 2,

wherein a strengthening web has been added at the base of the ribenvelope, the unfolding of the latter being represented in dashed lines;

FIG. 26 is a diagrammatic top plan view of apparatus which may besubstituted for that at the upper portion of FIG. 1 and may be employedin connection with another embodiment of the invention, wherein ribenvelopes are individually adhered to apertured portions of unpleatedrib-side paper;

FIG. 27 is a diagrammatic side elevation view of the apparatus of FIG.26-;

FIG. 28 is a perspective view of a portion of the ribside paper formedin the embodiment of FIGS. 26 and 27 showing the rib envelopesflattened;

FIG. 29 is a transverse sectional view thereof illustrating ribformation from the rib envelopes of the embodiment of FIGS. 26-28;

FIG. 30 is a diagrammatic perspective view of another embodiment of theinvention similar to that of FIG. 26 except that the gypsum slurry isintroduced into the individual rib envelopes directly rather than viaapertures in the unpleated rib-side paper; and

FIG. 31 is a diagrammatic perspective view of still another embodimentof the invention wherein the rib-side paper after formation of ribcontours therein is fed inline with the downstream supporting surfacesso that the ribs need not be temporarily flattened for purposes ofnon-rectilinear travel.

The apparatus of FIGS. 1 and 2 must of necessity be illustrateddiagrammatically because of its extreme length. For example, theapparatus to the right of point A may alone occupy as much as 25 to 50feet and the apparatus to the left of point A, including to the left ofpoint B, the important details of which are illustrated in subsequentfigures, may typically occupy 500 to 700 feet. Much of this length tothe left of points A and B is made up, however, of a conventionalfiat-belt conveyor system, e.g., 400 to 500 feet, and roller conveyorsystem, e.g., to 200 feet.

For orientation when reviewing the drawings, it should be kept in mindthat (with the exception of FIG. 31) the process of manufacturecommences at the right-hand side of the figure and the finished buildingboard exits at the left-hand side. In keeping with the object ofhigh-speed, high-volume continuous production, it should also be kept inmind that building board may be produced by the method and apparatus tobe described in detail at the rate of 40 to feet per minute.

Certain detailed aspects of the operation are not described orillustrated herein because such are the same as in conventional buildingboard manufacture or are otherwise well within the skill of the art. Aspecific description thereof would merely burden the specificationwithout adding anything to the knowledge of those skilled in the art.For example, no specific description is included herein as to theoperation of folding the edges of the face-side paper so as to form withthe rib-side paper an envelope for the fluid gypsum slurry. Techniquesand apparatus for same are already well known.

The specific embodiment of the apparatus shown in FIGS. 1 and 2 isdesigned to produce building boards of the type used to form the panelof FIG. 3. For orientation and illustration (but not limitation), thebuilding boards of FIG. 3 may, for example, have a length of 96 inches,a width of 48 inches and a thickness between ribs of inch. Seven ribsmay be present thereon, the centerlines of the seven ribs being located,respectively, 2 /2, 6 /2, 14 /2, 22%, 30 /2, 38 /2 and 46 /2 inches fromthe left-hand longitudinal edge. Each rib may have a height of inch, asmeasured from the rear side of the board or 1% inches as measured fromthe face side. Thus, all of the outermost surfaces of the ribs lay in acommon plane parallel to the plane of the face side of the board. Thewidth of the ribs at the outermost surfaces may be about A to 1% inches.At intermediate points in the rib cross-section, as is apparent, forexample, in FIG. 19, the width of the ribs may be substantially less,e.g., /2 to inch. As previously indicated, the aforementioned figuresand dimensions are illustrative only of a typical building board, andthe method and apparatus of the present invention are not limited to theproduction thereof.

Referring to FIGS. 1 and 2, two supply rolls of paper and 12 areprovided, the lower roll 10 being the source of the face-side paper weband the upper roll 12 being the source of the rib-side paper web. In thecompleted panel of FIG. 3, face-side paper is shown at 14 and rib-sidepaper is shown at 16.

The paper webs of supply rolls 10 and 12 may comprise conventionalgypsum wallboard paper known to those skilled in the art. Thus, forexample, the paper of supply roll 10 may be conventionalregular-strength or high-strength manila face paper, whereas the paperof supply roll 12 may be conventional news-lined rear-side paper. Othertypes of paper having the requisite strength, absorption, porosity andother required characteristics may also be employed, e.g., kraft backpaper, the paper per se not being part of the present invention. Ingeneral, however, the face-side and rear-side paper should have atensile strength in all directions no less than about 15 pounds perlineal inch, preferably no less than about 25 pounds per lineal inch.

The paper of supply roll 12 is wider than in conventional gypsumwallboard production in order to provide the additional paper requiredfor the subsequent formation of rib envelopes therein. Accordingly, whenforming a board having a finished width of approximately 48 inches andcontaining 7 ribs having a height of 78 inch each, such as illustratedin the panel of FIG. 3, the paper of roll 12 may initially have a widthof aproximately 60 inches.

Upon leaving roll 12, web 18 may be chamfered adjacent the edges, as inconventional practice, so as to provide a smooth mating surface whensubsequently overlapped and adhered to the face-side paper. Web 18 thenpasses between two dead bars with edge guides (not shown) to positionthe paper on centerline.

Paper web 18 may then optionally pass between creaser roll 20 and hardrubber backup roll 22 and between creaserroll 24 and hard rubber backuproll 26. The purpose of the creaser rolls is to provide fold-prone lineslongitudinally on the paper web to facilitate the subsequent folding'ofthe paper into pleats and rib envelopes.

Details of the creaser rol-ls 26 and 24 as well as the appearance of afragment of web 18 after being creased by both rolls are illustrated inFIGS. 4 and 5. The creases resulting from creaser rolls 2t and 24 are onopposite sides of the rib-side paper, as shown by fragments 28 and 30,because of the opposite direction of subsequent folding when formingpleats and/or rib envelopes.

As one skilled in the art will recognize, it is important that the paperhe kept substantially free of wrinkles to insure uniform spacing ofcreases. To this end, the'paper is maintained in a plane as creaserrails 20 and 24 push the sheet slightly into the resilient hard rubberbackup rolls 22 and 26, respectively, and supplementary bars (not shown)are employed to hold the edges flat. Other alternative or supplementarydevices such as cocked wheels or the like (not shown) may be employed ifexcessive wrinkling conditions are incurred.

Web 18 (optionally creased as above described) then passes over a convexsurface 32, e.-g., a bowed roller, and changes direction about 45.Convex surface 32 may, for example, comprise seven cylindrical rollers,each having a diameter of 6 inches and a length of 9 inches and mountedsideby-side so as to form a substantially continuous surface having acrown at the center of approximately /2 inch. In short, the rollers aremounted so as to approximate a circular arc having a chord spacedtherefrom at its center about /2 inch. Because the degree of convexityis so slight, it is not apparent in FIGS. 1 and 2. Convex surface 32 orthe position of its crown relative to the tangential approach of paperweb 18 is adjustable and is adjusted so as to induce a convergence inthe paper exactly matching the gathering of the pleats as hereinafterdescribed.

As it leaves bowed roller 32, paper web 18 is slightly crowned, theextent thereof depending on the adjustment of convex surface 32; and theensuing supporting surface 34 has a corresponding crown whichprogressively dissipates to a fiat surface as the paper exits therefrom.Thus, supporting surface 34 follows the natural contour of theconverging paper web as pleats are progressively formed therein.

Pleat formation in web 18 is accomplished by passing the weblongitudinally between moving surfaces 34 and 36, said support surfaceshaving longitudinal spans of about 16 feet and 18 feet, respectively. Asbest shown in FIG. 2, support surfaces 34 and 36 comprise a series ofspaced endless belts or chains with flat surfaces secured thereto. Inone embodiment, as suggested at 36' (the right side of FIG. 2), the flatsurfaces comprise a plurality of closely-spaced Delrin plastic plateletssecured to each of the chains so as to form a longitudinally continuous(although segmented) surface. In this embodiment the dimensions of theplatelets of surface 34 are about 1 /2 inches in the direction ofsurface travel, 3 /2 inches trans verse to the direction of surfacetravel, and about /3 inch thick. The corresponding dimensions for theplatelets of surface 36 are about 1 /2, 4, and /8 inches, respectively,except in the case of the single narrow edge section shown at the top ofFIG. 2, where the platelets are only about 2 inches transverse to thedirection of surface travel.

At the right side, as viewed in FIG. 2, the endless belts or flat-topchains comprising support surface 34 are spaced substantially from oneanother as indicated at position 38. The spacing is progressivelyreduced so that at position 39 substantially no spacing exists and anunbroken transverse span results at the discharge end.

Upper surface 36 differs from surface 34 in that the individuallongitudinal sections thereof are fewer in number and do not completelyconverge, thereby providing space for the pleats or rib envelopes whichare induced in the paper web therebetween. It should be understood,however, that the top and bottom surfaces 34 and 36 preferably travelthe same laterally-convergent paths having a common axis of convergence.To assure pleat formation between each section of surface 36 as thesections con verge, the contacting surfaces thereof have a highcoefficient of friction so as to securely grip the paper web. In aspecific embodiment this is readily accomplished by cementing grit, sandpaper, emery paper or the like to the smooth surfaces of the Delrinplastic platelets, e.g., 36- grit Carborundum paper. Thus, as thesections of upper surface 36 converge toward one another, the portionsof web 18 therebetween must fold or otherwise overlap. It is this actionwhereby the pleats are induced.

Proper pleat formation is controlled by means of pleat median strips 40and a series of straddling rollers, e.g., 41, 41, 41", etc., on supports42, 42', 42", etc., positioned between each longitudinal section ofsurface 36. These are illustrated in FIGS. 6, 7 and 8, which show insection progressive pleat formation. FIG. 6 is a section view ofsurfaces 34 and 36 adjacent the right extremity of FIGS. 1 and 2. FIG. 7is a section view at a point approximately midway between the right andleft extremities of surfaces 34 and 36. FIG. 8 is a similar view takenadjacent the left extremity of FIGS. 1 and 2.

In FIGS. 6, 7 and 8, the plastic platelets forming surfaces 34 and 36are secured to connecting links 43 and 44, respectively, which are partof moving chains 45 and 46, respectively, chain guides for chains 46being indicated at 47 and longitudinal support bars for the platelets ofsurface 34 being indicated at 48. It will be noted from a comparison ofFIGS. 6, 7 and 8 that the sections of surface 34 progressively convergeuntil the gap therebetween substantially disappears. At the same time,the sections gripping surface 36 also converge, the spacingthere'between being suflicient, however, to permit formation of the ribenvelope.

The pleat median strips 40 are continuous contoured bars extendingalmost the entire length of surface 34 between the individual sectionsconstituting surface 36. They have, for example, a height of A inchinitially, as shown in FIG. 6; a maximum height corresponding to thepleat fold at about midpoint in longitudinal travel, as shown in FIG. 7;and a final upraised thin portion just prior to the point of exit asshown in FIG. 8. The width of pleat median strip 40 from the lead orupstream end (FIG. 6) to the mid-point (FIG. 7) is as wide as thedesired inside of the top of the pleat. From mid-point to the trailingor downstream end (FIG. 8), the width narrows slightly and the edges arerelieved to allow the pleat to fold under its own flat top. Each pleatmedian strip 40 is anchored at the lead end only and floats on the lowersurface 34.

Astraddle of pleat median strip 40 and spaced at periodic intervals,e.g., every 4 /2 to inches, are the small rollers 41, 41, 41", etc.,e.g., tapered rollers having an average diameter of about 1% inches.Such rollers are disposed and aligned so as to produce creases along theneck of the pleat, as indicated in FIGS. 6, 7 and 8. Where the paper hasoptionally been grooved to form fold-prone lines, the rollers wouldnormally be aligned to follow the corresponding grooves. Thus, bycareful positioning of the rollers, the pleat can be made to folduniformly and evenly. Flatteners may be optionally spaced along theapparatus above the pleat median strips to keep the top of the pleatflat. Bars, rollers, rolling discs or the like (not shown) may, forexample, be used.

At the discharge end, pleat-flattener rolls 50 (see FIGS. 1 and 2) arelocated to give the final flattened shape to each pleat. As illustratedin the magnified view of FIG. 9, the primary function of pleat-flattenerrolls 50 is to flatten the pleats so that the pleated paper maysubsequently travel in non-rectilinear directions without significantdistortion. These rolls are typically rubber faced and may be adjustableso as to act as guide rolls as well as press or flattening rolls.

The outer edges of the sheet, which are not converged *by top grippingsurface 36 may be tucked under the pleat by using small cocked rubbertraining rollers (not shown). Alternatively, additional edge sectionsmay be added to gripping surface 36 so as to form the pleats in the samemanner as the intermediate pleats are formed in FIGS. 6, 7 and 8, theparticular technique employed being a matter of design and/ or costexpediency,

Paper web 18 with flattened pleats leaves the pleating and conveyorsystem formed by surfaces 34 and 36 and passes over concave surface 52,changing direction about 45 in so doing. Concave surface 52 may comprisea series of side-byside rollers similar to those used to form convexsurface 32, except that the concave portion thereof is tangential topaper web 18. The degree of concavity employed is adjustable and isadjusted so as to eliminate any convergent tendencies in web 18, wherebythe web leaves concave surface 52 in a parallel stream.

In certain specific embodiments it is important to keep the tension inpaper Web 18 as it leaves the pleat-forming assembly substantiallyconstant, e.g., about l30-170 pounds pull (spread over the 48-inchapproximate width). Tension is readily maintained by, for example, usinga drive on the pleater assembly, e.g., an Adjustospede electric motor,the speed of which is responsive to the force of the pleated paperagainst concave surface 52, and to incipient changes in the force.Accordingly, if tension starts to drop below the desired level, thespeed of the pleater assembly is at least momentarily decreased, rela- 8tive to the speed of the subsequent board-forming assembly, hereinafterdescribed, until paper tension rises to desired level. Conversely, ifpaper tension starts to increase above desired levels, the speed of thepleater assembly is increased relative to the subsequent board-formingassembly until paper tension decreases to the desired level.

The traverse of pleated paper Web 18 from the pleatforming assembly tothe board-forming assembly is made via lateral bars 54, 56 and 58 andweb guide roll 60. Bars 54, 56 and 58 are disposed so that the path ofpaper web 18 is not changed more than about 5. These bars help tomaintain pleat integrity during traverse of the paper to theboard-forming assembly. They may be supplemented by edge bars or thelike (not shown) to prevent the outer pleats from spreading. Web guideroll 60 is used to position the pleated paper Web 18 on master-formingroll 62, thereby assuring that the pleats are aligned with the recessesin forming roll 62, hereinafter described in detail.

As shown in FIG. 10, forming roll 62 comprises a plurality of individualcylindrical sections 64, 66, etc., mounted in spaced relationship on arotatable shaft 68. Each of the pleats in paper web 18 is aligned with arecess in forming roll 62 such as illustrated at 70 in FIG. 10. Theleading portions of vacuum manifolds 72 are inserted into recesses 70 toinsure that the rib raises fully at this point.

The principle involved is that of forming the rib and filling it withgypsum where it is most readily accomplished. This is at the nip wherethe slurry head collects as on a conventional board machine.Accordingly, as calcined gypsum slurry 74 from source 76 is deposited onface-side web 78 from supply roll 10 a head of gypsum slurry 80 collectsat the point of spaced convergence of rib-side web 18 and face-side web78. As in conventional wallboard production, the vertical position offorming roll 62 above the machine table 81 normally gauges the volume ofslurry introduced between the face and rear-side papers, otherconditions being the same.

As shown in FIGS. 1 and 2, the ribs which are formed are supported orheld up by vacuum means for the first 3 to 8 feet past the centerline offorming roll 62. These vacuum means include the aforementioned vacuummanifolds 72 and supplementary manifolds 82 and 84 and 86, all of whichdraw from a common vacuum source 88, which is supported from frame 90.The level of vacuum typically employed corresponds to at least about 20inches of water, with a preferred vacuum level of at least about 40inches of water, e.g., about 60 inches of water, and may rangesubstantially higher, e.g., about inches or more.

As indicated in FIGS. 1, 2 and 10, the first section of manifold 72 islocated ahead of the forming roll centerline. It has been found thatthis first 6 inches or so of manifolding is of considerable importancein the rib forming operation. The subsequent vacuum manifolding isprimarily necessary for rib support, rather than rib formation. Edgeribs in particular usually require this vacuum support, and in someembodiments the vacuum manifolds for the edge ribs may be extendedbyeond the manifolds for the intermediate ribs, e.g., an additional 2 or4 feet.

Functional equivalents for rib-forming roll 62 are shown in FIGS. 11through 14. In FIG. 11 a forming plate 94 with recesses for vacuummanifolds 96 and 98 are substituted for forming roll 62. In FIGS. 12 and13 a system of spaced continuous flexible belts 100 travel aboutrotatable cylinders 102 and 103 mounted on shafts 104 and 105,respectively, and thereby provide a contour surface containing recesses106 into which vacuum probes 107 with nozzles 108 are inserted. Thedistance between shafts 104 and may typically be about 2-10 feet ormore, e.g., about 4 /2 feet. This embodiment has the advantage ofreadily providing positive support for the ribs for any desireddistance. In FIG. 14 a combination of conventional cylindrical roll 110and forming roll 112 (recessed at rib locations) with intermediatevacuum manifolding 114 is employed. In each embodiment the applicationof vacuum is employed to assist in opening flattened pleats to form ribenvelopes, as indicated in dashed lines in FIG. 15, and to assist infilling the rib envelopes with calcined gypsum slurry. In addition,supplemental vacuum manifolding, such as manifold 98 in FIG. 11, may beemployed to help support the resulting ribs.

It is also possible to form ribs by admitting the proper volume ofslurry between a face-side paper and rib-side paper, which is preferablypleated, and then forcing the fluid slurry upward at rib locations,while the slurry still retains a fluid character, by flattening theareas between desired ribs. While this method appears to be quitesimple, it requires careful control and is not in fact has easilyaccomplished as in the methods already described wherein recessedsurfaces with vacuum assistance are employed. These and other techniquesfor forming ribs are within the skill of the art in the light of thepresent disclosure.

As a supplement to or substitute for vacuum techniques for assuring ribformation, vibration techniques applied at or adjacent to the area ofrib formation may also be used. For example, vibrator means 115 in FIG.1 may be employed to apply vibratory pulses to table 81 and thereby tothe fluid gypsum slurry and associated structures. In a typicalinstallation, a conventional vibrator or pulsator having a frequency of,for example, 1000 to 50,000 cycles per minute, e.g., 10,000 cycles perminute, may be secured to the table immediately upstream, downstream orunderneath the master-forming roll 62, preferably within 10 feet of themaster-forming roll. Vibration techniques are very advantageouslyemployed in connection with certain embodiments such as where the fluidgypsum slurry must pass through obstructions as represented byreinforcing webs, apertured rear-side paper, or the like, as hereinafterdescribed.

While the rib structure is being formed as above described, the board isdrawn over fiat table 81 for a distance of, for example, about 2 to 12feet past the masterforming roll, e.g., about 3 feet, to insure thatthere are no irregularities in thickness which might otherwise resultfrom use of a conveyor belt system or the like at this critical point inboard formation. Flattener plates (not shown) between the rib supportmanifolds 72, 82, 84 and 86 may also be employed. These flattener platesmay be adjustable so as to provide control of between-rib thickness.

Gauging means (not shown) for tapering the longitudinal edges of theboard may also be provided, as in conventional practice. For example, tocompensate for the thickness of joint tape and cement used whenadjoining boards are conventionally finished, a taper commencing atabout 2% inches to 2% inches in from the edge on the face side andresulting in a reduction in edge thickness of about 0.035 to 0.040 inchmay be provided.

As previously indicated, the primary function of the rib-forming roll 62and vacuum manifolding system represented by manifolds 72, 82, 84 and 86is to expand the pleats into rib envelopes, to fill these rib envelopeswith approximately the correct amount of calcined gypsum slurry, and toprovide momentary support for the ribs once formed. Final rib shaping,however, occurs further downstream, e.g., between positions A and Bshown in FIGS. 1 and 2, where the gypsum slurry has begun to set up butis still'plastic. This is accomplished by means of a series of contourbars, as illustrated in FIGS. 16 and 17, and by rib-height gauging roll116 as shown in FIGS. 1 and 2 and further illustrated in FIG. 18.

Thus, as the rib structure leaves flat table 81, it is picked up byelongated conveyor belt 118, which is .traversed at spaced intervals bya system of contour bars shown in FIGS. 16 and 17. In a typicalembodiment 10 three sets of contours are located at successivelyincreasing intervals downstream from master-forming roll 62. The contourbars comprise a transverse supporting bar on which is movably securededge-support bars 122, between-rib flattening plates 124 and ribside-supports 126. As shown in FIG. 17, the top of the rib itself issomewhat rounded as it passes through the contour bars.

Several sets of such bars are employed because experience has shown thatthe rib structure tends to slump slightly or otherwise become somewhatmisshapened for a substantial distance downstream of the master-formingrolls and the supporting vacuum manifolds. If such slumping were allowedto continue and correction thereof attempted in one single shaping stepafter suflicient set had been achieved, harmful stresses in the gypsumand paper would result, resulting in deleterious strains and inferior orunusable final products. The problem is highlighted by the fact that atthis point in the over-all operation the covering paper is quite wet andthus comparatively weak. The stepwise correction of the slumping problemas it occurs by means of a series of cont-our bars at spacedlongitudinal intervals avoids this difliculty.

As aforementioned, rib height is a critical consideration and must besubstantially uniform as measured from the face side. In the presentapparatus and method, uniformity is obtained by forming all ribs up toabout /a inch too high and then, while the gypsum is still plastic butotherwise self-supporting, flattening all of them to the same height bymeans of thickness gauging roll 116. Thus, as shown at the left side ofFIG. 1 and on an enlarged scale in FIG. 18, rib height is purposely madeexcessive as it approaches the thickness gauging roll 116 but iscorrectly dimensioned after passing thereunder. To insure uniformgauging, backup roll 128 is disposed opposite the thickness gauging rollto prevent any sagging in supporting belt 118.

Side rollers (not shown) may optionally be employed to support the sidesof the ribs as the ribs pass beneath thickness gauging roll 116. Theserollers prevent the sides of the ribs from necking inward or otherwisecollapsing or fracturing as a result of the stresses resulting from therib-height gauging operation. After the rib has passed beneath thethickness gauging roll, it has the desirable final contour shown in FIG.19, including an enlarged flat contacting surface for adhesive bonding.

After the gypsum has substantially fully set, it may be transverselysegmented into desired lengths by means of cutting apparatus such asillustrated in FIGS. 20 and 21. The rotational speeds of lowersegmenting assembly 130 and upper segmenting assembly 132 arecoordinated with each other and with the speed of the ribbed board 134,which is supported on rolling members 136 and 138, so that only minimumrelative movement between the board and blades 140 and 142 occur as theblades penetrate the board.

The design of penetrating blades 140 and 142 has been found to be mostcritical. Blades 140 of lower assembly 130 may be of conventionalsaw-toothed design as shown in FIG. 21. Upper blade 142 must becontoured at rib locations as shown in FIG. 21. Otherwise rib smashingand other difficulties may be encountered.

In a specific example, blades 140 and 142 may be made from the bestgrade of Swedish wood band saw steel having a Rockwell hardness of C42to C44 and a thickness of 0.0329 inch. There may be 5 canted teeth perinch, the tip to root distance being 0.150 inch. Where blade 142 iscontoured at rib locations, the [contoured portion may have a width of0.80 inch at the lower extremity and a width of 0.40 inch at the upperextremity, the tip-to-tip vertical distance being about 0.85 inch. Thedimensions in any particular case are, of course, a function of the ribconfiguration. In general, the operation of the segmenting assembliesand the shape or contour of the blades are designed so as to assurecomplete severance of the paper covering on both surfaces of the board,including the ribs.

1 1 This normally requires that the blades penetrate at least to theroot of the teeth and that the teeth of the upper and lower bladesintermesh. Once the paper covering is severed, the gypsum, includingthat in the ribs, readily fractures without any substantial additionalpenetration by the blades.

After segmenting the board, the extremities of the ribs may optionallybe removed so as to provide recesses for supporting splines,installation plates or channels, or the like. Removal may be readilyaccomplished as indicated in FIGS. 22 and 23 wherein router 144, asillustrated in FIG. 24, is passed across the board at the extremitythereof. Accordingly, router 144 may be passed transversely adjacent theends of the board, either with the router axis parallel to the ribs asshown in FIG. 22, or with the router axis erpendicular to the ribs asshown in FIG. 23. In a typical operation approximately 1% inches of therib extremities are removed at each end of the building board.

In an alternative embodiment, the routing of rib ends is accomplishedprior to segmenting of the board. In such embodiment the routerpreferably removes approximately 3% inches of the rib, following whichthe board is segmented midway in the rib-free portion. This alternativeembodiment has the advantages of reducing the number of routingoperations and, in certain instances depending on relative clearances,permitting the use of conventional upper cutting blades, rather than theprofile blade such as blade 142 of FIG. 21.

The routing operation should take place only when the paper cover issufficiently dry to resist tearing resulting from the routing stresses.Accordingly, it is sometimes desirable to postpone the routing operationuntil after kiln drying of the board. Since kiln drying normally occursafter segmenting the board, routing prior to segmenting may be feasibleonly under special operating procedures.

In still another embodiment of the present invention, the juncture ofthe ribs with the rear side of the board, at least in the case of theedge-adjacent ribs, is reinforced by the addition of a reinforcing web150 from supply source 151 (FIG. 1). This web may be added asillustrated in FIG. 1 by feeding same tangential to master-forming roll62 at the various rib locations. The position of reinforcing Web 150relative to the pleated rib-side paper is illustrated in FIG. 25.

Such reinforcing web may take the form of an openlace-work of strands ofa suitable material, e.g., natural or synthetic fibrous materials, suchas various plastics, e.g., polyethylene, polypropylene, or the like;glass; rayon; Dacron; or equivalents thereof. The web may also c-omprisean apertured sheet material or fabric, e.g., paper, the variousaforementioned natural and synthetic materials, and equivalents thereof.

In another embodiment the strengthening web might merely compriseindividual spaced strands or strips of such materials transverse to thelongitudinal direction of the ribs. Such uni-directional reinforcementis feasible because it is only in a lateral direction that the papercovering on the rib side does not provide substantial strengthening allacross the board.

Where such strengthening webs are not adhered to the inside of the papercover of the rear side, the shape, texture or nature of its surfacethereof must be such as would hinder slippage through the set gypsum inwhich it is imbedded. Otherwise, the web would tend to slip and notabsorb the tensile forces to which the structure might be subjected.

Whatever the strengthening means, it must be penetrable by a fluidslurry of calcined gypsum so as to provide a path for entry of same intothe rib configuration during manufacture of the board. Such paths alsoas sure partial continuity of the gypsum and minimize possible cleavageor slippage planes in the structure. As already indicated, the vibratoryapparatus 115 shown in FIG. 1 may be employed to assure rapid passage ofthe gypsum through the web into the rib envelopes.

Still another embodiment of the present invention is illustrated inFIGS. 26 through 29. In this embodiment individual rib envelopes 152,which are pleated and flattened, are fed from supply roll 154 and .areadhered to rear-side paper 156 from supply roll 158. Rear-side paper 156is apertured coextensive with the desired rib locations, and the edgesof the rib-side envelopes 152 are adhere adjacent the apertures 159 bymeans of suitable contact adhesives or the like. After passing betweenpressure rolls 160 and 162 and around direction-changing roll 164, theremaining portion of the process may be as indicated in the lowerportion of FIG. I, beginning with lateral bar 54.

In the embodiment of FIGS. 26 through 29 the paper webs intermediateapertures 159 in the rear side paper are in tension when the rear sideof the board is convexly flexed laterally. The ability of the paper websto absorb the tensile forces at the rib locations supplements thetensile strength of the gypsum.

The apertures 159 are for the same purpose as the openings in thereinforcing web of FIG. 25, i.e., to provide a path for flow of gypsumslurry into the rib envelopes during manufacture and to providecontinuity to the gypsum structure without slippage or cleavage planes.The size of the openings is not critical so long as a gypsum slurry canrapidly flow therethrough. In practice, circular apertures of flt-inchminimum diameter are preferred. Because of the strength-i-mpartingfunction of the web and the' need to avoid tearing thereof duringmanufacture of the board, the minimum crosssection of the web isnormally not reduced to less than 20 percent of the total. Thus, forexample, in the case of a web having circular apertures of l-inchdiameter, the inter-aperture web should be at least A1 inch. Theminimum-size inter-aperture web is, of course, a function of theinherent strength of the web material, higher strength paper, forexample, permitting smaller webs.

Still other embodiments of the present invention are schematicallyillustrated in FIGS. 30 and 31. In FIG. 30, conventional unpleated,unapertured rear-side paper 166 from a supply roll thereof (not shown)is fed via forming roll 168 in spaced relation from face-side paper 78,thereby initially forming what appears to be conventional gypsumwallboard. Rib envelopes 170 from supply rolls 171 are subsequentlyadhered to the rear side paper by, for example, conventional contactadhesive, a fluid gypsum slurry being injected into the rib envelopes asthey are adhered to the rear side paper. Accordlngly, a fluid gypsumslurry from supply source 172 IS injected from gypsum manifold 174 intothe rib envelopes 170 via nozzles 176. The remaining steps of theprocess and apparatus may then take the form of the embodiments alreadydescribed or equivalents thereof, such being represented schematicallyin FIG. 30 for simplicity by zone 178.

In FIG. 31 the rear-side paper is fed in line with the subsequentboard-forming operation. Thus, the rib envelopes need not be initiallyflattened in order to permit non-rectilinear travel. Accordingly,rib-side paper 180 from source 182 passes through rib envelope formingzone 184, which may take the general form of the first half of the ribpleater shown in the upper portion of FIG. -1, the first half pointbeing shown in section in FIG. 7. Once the rib envelopes are properlyformed, the paper may be fed directly (without flattening of the ribenvelopes) in a straight line to board-forming zone 186 wherein it isaligned with face-side paper 188 from supply source 190, fluid gypsumslurry from source 192 being fed via distributor 194 therebetween. Inshort, in FIG. 31 the rib-side paper, not the face-side paper as shownin the other illustrated embodiments, is fed in alignment with the boardsubsequently to be produced.

up with a smooth rapid motion.

The face-side paper convergently joins it from below, non-rectilineartravel thereof not being a problem.

In all of the above described embodiments, the specific design of'theapparatus is tailored in part to the assumed characteristics of thecalcined gypsum slurry and/or vice versa. The calcined gypsum slurry istypically a cementitious slurry of calcium sulfate hemihydrate, water,starch, foam, fibers, set-accelerating reagents, etc., as is well knownto those skilled in the art. The characteristics of the slurry may bevaried considerably depending upon the particular formulation employed.Among the characteristics important to successful operation of thepresent method and apparatus are slump and set-time characteristics.

Slump is a rough measure of fluidity of the gypsum slurry; and it isapparent from the detailed description above that once the rib structurehas been formed, the gypsum slurry must have suificient resistance toflow so that the rib structure does not collapse completely whenunsupported. The slump of the slurry is therefore carefully controlledby, for example, adjusting the amount of water in the formulation, sothat the ribs, once formed, will resist collapse.

The slump characteristics of a particular formulation may be determinedby taking a fresh sample of gypsum slurry as it is discharged from theslurry mixer and quickly pouring same into a clean, oiled2-inch-diameter, 4- inch-high brass cylinder which is supported on aclean, dry, 6-inch-square glass plate. After filling the cylinder, theslurry should be puddled with a spatula and the excess screeded offWithout dropping any on to the glass plate. The cylinder is thenimmediately raised straight The time elapsed between discharge of thegypsum from the mixer and raising of the cylinder should not exceed 10seconds. The average diameter of the gypsum patty formed on the glassplate after the cylinder is raised provides a measure of slump. Inpractice, for example in the apparatus of FIGS. 1 and 2, it has beenfound necessary to control the slump so that the average diameter of thepatty does not substantially exceed about inches and is preferably less,e.g., not more than about 4 /2 inches.

Final set time may be considered for present purposes as thetimerequired for the gypsum to assume substantially the dihydrate. formalthoughexcess (free) moisture need not yet be removed. At final set thegypsum is, of course, no longer plastic and is characteristically hard.Final set time ,is of particular importance in the present method andapparatus because certain of the operations must be completed wellbefore final set has occurred, whereas other operations must becompleted substantially at or after final set. For example, the step offilling the rib envelopes with gypsum slurry, which might be termed therib-filling step, must be completed when the gypsum slurry still retainssome substantial degree of fluidity, i.e., within about 5 percent of thefinal set time, preferably within 3 percentof the final set time. Thesubsequent rib-shaping step, including rib contouring and ribheightgauging, must be completed while the gypsum still retains somesubstantial degree of plasticity, i.e., within about 40 percent of thefinal set time. Segmenting of the board should occur when the board issubstantially fully set and thus hard or thereafter.

As a specific example, the embodiment of FIGS. 1 and 2 may employ agypsum slurry 74 having a slump, as above determined, of about 4 inchesand a final set time of about 5 minutes (300 seconds). The board isproduced on the apparatus at the rate of about 100 feet per minute.

It is apparent that the rib-filling step carried out by master-formingroll 62 and vacuum manifold 72 is completed well within 3 percent (9seconds) of the final set time, which. corresponds to a board traveldistance of about 15 feet. Three sets of contour bars as shown in FIG.16 are located, respectively, at distances of 20 feet,

44 feet and 84 feet from master-forming roll 62. Gauging roll 116 islocated 150 feet from master-forming roll 62, the distance betweenpoints A and B in FIG. 1 therefore approximating about 130 feet. Thus,it is also apparent that the rib-shaping step is completed well within40 percent seconds) of the final set time, which corresponds to a boardtravel distance of 200 feet. The segmenting assembly of FIG. 20 islocated approximately 600 feet from the master-forming roll. It takesthe board 6 minutes to reach this point; and with a final set time of 5minutes, it is apparent that the gypsum is already fully set before thesegmenting operation.

While shortening of the setting time could substantially decrease thelength of the board line herein described, the setting time can not becut too greatly because blistering problems often result. These andother considerations are well recognized by those skilled in the art.

While not specifically described herein, it should be understood thatafter segmenting the ribbed board, the board is dried in a kiln toremove excess (free) moisture. This operation is similar to thekiln-drying operation employed in the production of conventionalwallboard. Because a ribbed board has a non-uniform cross-sectionalarea, however, special care must be taken to assure adequate dryingwithout burning or calcining the board. Proper rib design is animportant consideration in meeting such drying requirements. In theembodiment of FIGS. 1 and 2 the drying operation may be carried out, forexample, for a period of 1 hour in a continuous, multilayer kiln inwhich forced air is introduced at a temperature of about 500 \F.

From the above description of the several specific embodiments, it isapparent that the objects of the present invention have been achieved.It should be understood, however, that while the method and apparatus ofthe present invention have been described with particular reference tothese particular embodiments, such reference is merely illustrative, andthe inventive concept is not necessarily limited thereto. For example,those skilled in the art will recognize that while the present methodand apparatus are described herein in connection with the formation of abuilding board with ribsof certain sug- :gested cross-sections, suchmethod and apparatus may also be employed to form protrusions of otherdesired crosssections; and the term rib used herein may be construed toencompass same. Many alternative modifications will be apparent from theabove description to those skilled in the art. Such other alternativesare considered within the spirit and scope of the present invention, andcoverage thereof is intended by this application.

Having described the invention, what is claimed is:

1. An apparatus for the continuous manufacture of ribbed building boardor the like from opposed continuous webs of paper having parallel edges,one web being a face-side Web, the other web being a rib-side web withlongitudinal folded portions corresponding to desired 10- cations of aplurality of ribs, which apparatus comprises in combination:

(a) a lower elongated support surface for said faceside Web whereby saidface-side web may be flatly disposed thereon;

(b) an upper rib-forming surface for said rib-side Web disposed inopposed and spaced relation above and adjacent one extremity of saidlower elongated support surface, said rib-forming surface having curvedportions to effect spaced convergence of said rib-side web with saidface-side web and also having longitudinal recesses thereincorresponding to desired locations of a plurality of ribs;

(c) a source of supply of calcined gypsum slurry disposed to provide ahead of slurry just ahead of the vertical passage constituted by thespace between said lower elongated support surface and said upperrib-forming surface;

(d) d-riving means associated with said lower elongated support surfacewhereby face-side and rib-side webs with gypsum therebetween which aredisposed thereon are moved longitudinally; and

(e) cutting means adjacent the other extremity of said support surfacewhereby the resulting building board may be transversely severed.

2. The apparatus of claim 1 including vacuum means disposed so as tocreate .subatmospheric pressures in at least a portion of said recessesof said rib-forming surface.

3. The apparatus of claim 1 including contour surfaces disposed inspaced relation above said lower elongated suport surface downstream ofsaid upper rib-forming surface so as to shape the ribbed surface of thebuilding board.

4. The apparatus of claim 1 including a gauging surface disposed inspaced relation above and transverse said lower elongated supportsurface downstream of said upper rib-forming surface and disposed so asto limit rib height above the face-side paper to a predeterminedmaximum.

5. The apparatus of claim 1 wherein said cutting means comprises opposedupper and lower serrated blades, the upper blade having serrated notchestherein spaced to correspond to rib locations.

6. The apparatus of claim 1 wherein said lower elongated support surfacecomprises a stationary flat surface adjacent said upper rib-formingsurface communicating with an elongated, moving, fiat conveyor belt.

7. The apparatus of claim 1 including routing means disposed for removalof a portion of the ribs after formation thereof.

8. An apparatus for the continuous manufacture of ribbed building boardor the like having a gypsum core and paper envelope, which apparatuscomprises in combination:

(a) a source of a continuous web of face-side paper;

(b) a source of a continuous web of rib-side paper, the rib-side paperhaving longitudinal folded portions corresponding to desired locationsof a plurality of ribs;

(c) an elongated, lower, flat support surface for said face-side paperincluding longitudinally moving portions whereby said face-side paper isflatly disposed on and conveyed longitudinally;

(d) an upper rib-forming surface for said rib-side paper disposed above,opposed to, and in spaced relation from said support surface adjacentone extremity thereof, said rib-forming surface having curved po-rtionsto effect spaced convergence of said rib-side web with said face-sideweb and also having longitudinal recesses therein corresponding todesired locations of a plurality of ribs with vacuum means disposed soas to create subatmospheric pressures in at least a portion of saidrecesses;

(e) a source of supply of calcined gypsum slurry disposed to provide ahead of slurry ahead of the vertical passage constituted by the spacingbetween said support surface and said rib-forming surface;

(f) contour surfaces in spaced relation above said support surfacedownstream of said rib-forming surface and disposed so as to shape theribbed surface of the building board;

(g) gauging surface disposed in spaced relation above and transversesaid support surface downstream of said rib-forming surface and disposedso as to limit rib height above said support surface to a predeterminedmaximum; and

(h) severing means adjacent the other extremity of said support surfacewhereby the resulting building board may be transversely segmented intodesired lengths, said severing means comprising opposed upper and lowerserrated blades, the upper blade having serrated notches there-in spacedto correspond to rib locations.

9. An apparatus for the continuous manufacture of ribbed building boardor the like from opposed continuous webs of paper having parallel edges,one web being a face-side web, the other web being a rib-side Web withlongitudinal folded portions corresponding to desired 10- cations of aplurality of ribs, which apparatus comprises in combination:

(a) a lower elongated support surface for said faceside web whereby saidface-side web may be flatly disposed thereon;

(b) an upper rib-forming surface for said rib-side web disposed inopposed and spaced relation above and adjacent one extremity of saidlower elongated support surface, said rib-forming surface havinglongitudinal recesses therein corresponding to desired locations of aplurality of ribs;

(0) a source of supply of calcined gypsum slurry disposed to provide ahead of slurry just ahead of the vertical passage constituted by thespace between said lower elongated support surface and said upperrib-forming surface;

(d) driving means associated with said lower elongated support surfacewhereby face-side and ribside webs with gypsum therebetween which aredisposed thereon are moved longitudinally; and

(e) cutting means adjacent the other extremity of said support surfacewhereby the resulting building board may be transversely severed.

References Cited by the Examiner UNITED STATES PATENTS 1,353,512 9/1920Baumgartl 156-347 X 1,493,899 5/192A Routt 156347 1,970,029 8/1934Brunner et al. 156-347 EARL M. BERGERT, Primary Examiner.

M. SUSSMAN, Assistant Examiner.

1. AN APPARATUS FOR THE CONTINUOUS MANUFACTURE OF RIBBED BUILDING BOARDOR THE LIKE FROM OPPOSED CONTINUOUS WEBS OF PAPER HAVING PARALLEL EDGES,ONE WEB BEING A FACE-SIDE WEB, THE OTHER WEB BEING A RIB-SIDE WEB WITHLONGITUDINAL FOLDED PORTIONS CORRESPONDING TO DESIRED LOCATIONS OF APLURALITY OF RIBS, WHICH APPARATUS COMPRISES IN COMBINATION: (A) A LOWERELONGATED SUPPORT SURFACE FOR SAID FACESIDE WEB WHEREBY SAID FACE-SIDEWEB MAY BE FLATLY DISPOSED THEREON; (B) AN UPPER RIB-FORMING SURFACE FORSAID RIB-SIDE WEB DISPOSED IN OPPOSED AND SPACED RELATION ABOVE THEADJACENT ONE EXTREMITY OF SAID LOWER ELONGATED SUPPORT SURFACE, SAIDRIB-FORMING SURFACE HAVING CURVED PORTIONS TO EFFECT SPACED CONVERGENCEOF SAID RIB-SIDE WEB WITH SAID FACE-SIDE WEB AND ALSO HAVINGLONGITUDINAL RECESSES THEREIN CORRESPONDING TO DESIRED LOCATIONS OF APLURALITY OF RIBS; (C) A SOURCE OF SUPPLY OF CALCINED GYPSUM SLURRYDISPOSED TO PROVIDE A HEAD OF SLURRY JUST AHEAD OF THE